Field of the Invention
The present invention relates to a dual coating method for an electrode, and more particularly, to a dual coating method for an electrode, which realizes coating of an electrode for a battery.
Description of the Related Art
Secondary batteries are rechargeable unlike primarily batteries, and also, the possibility of compact size and high capacity is high. Thus, recently, many studies on secondary batteries are being carried out. Such a secondary battery is manufactured in a shape in which one battery cell is packaged in a pack form or a pack shape in which several tens of battery cells are connected to each other. As a result, secondary batteries are being widely used for power sources for driving motors of vehicles.
Electrode slurry in which an active material and a conductive material are mixed is applied to metal foil and then dried at a high temperature to perform a pressing process, thereby manufacturing an electrode of a secondary battery. A slot die coater for producing an electrode is a device for applying electrode slurry to metal foil.
That is, the slot die coater denotes a device in which a liquid fluid (slurry, an adhesive, a hard coating agent, ceramic, etc.) having fluidity is supplied between upper and lower slot dies by using a pulse-free pump or piston pump to apply a fluid supplied from a liquid supply pipe to a uniform thickness in a width direction with respect to an advancing direction of an object to be coated such as fabrics, films, glass plates, and sheets. The slot die coater for producing the electrode may be a device for applying a slot die coater to produce an electrode, i.e., a device for applying electrode slurry that is a supply fluid to metal foil to produce the electrode for the secondary battery.
Since the electrode slurry varies in flow rate in a width direction thereof according to process conditions and the shape of the slot die, it is necessary to adequately design a shape of each portion of the slot die coater for producing the electrode so at to obtain a coating layer having a uniform thickness.
An active material and a conductive material may be mixed in the electrode slurry at a high mass fraction to reduce a time taken for the drying process and secure productivity of the electrode. Thus, the electrode slurry may have high viscosity. The electrode slurry may be stagnant or have a very low flow rate according to a shape of a flow path in all sections from a mixing tank for storing and supplying the electrode slurry to the slot die coater for producing the electrode.
An electrode plate of a secondary battery and a coating apparatus for the electrode plate of the secondary battery according to the related art are disclosed in Korean Patent Registration No. 10-0646550.
The secondary battery according to the related art may be generally manufactured through single-layer coating using a single kind of electrode slurry.
However, the above-described method may have limitations such as crack due to a high curvature at a winding core because a single layer is uniformly coated and then wound to assemble a cell such as a circular cell.